Visual short-term memory is crucially important for tasks significant in infancy such as developing hand-eye coordination and associating words with objects. Thus, understanding infants' short-term memory abilities will add significantly to our understanding of normal development. Unlike long-term memory, which has a virtually unlimited capacity, short-term memory has a very limited capacity, and this has serious consequences for many other aspects of cognition. For example, reduced short-term memory capacity may lead a developing system to focus on smaller chunks of the input, facilitating the acquisition of language and other cognitive abilities. Thus, understanding of infants' short-term memory abilities is important for understanding the general constraints on cognitive development. The goals of the proposed project are to develop sensitive procedures to assess short-term memory in infancy and to use those procedures to determine how infants' short-term memory abilities are similar to and different from those of older children and adults. In the first year, two experiments will be conducted to evaluate the usefulness of two change-detection procedures for assessing infants' visual short-term memory. In one procedure, infants' preference for changing over non-changing stimulus streams will be observed. The logic is that if infants can remember the items in the display, they will detect the change and prefer (i.e., look longer at) streams that change over those that remain the same. The second procedure will evaluate infants' ability to learn that changing (or non-changing) streams are associated with a reward as indicated by their accurately turning their head toward the source of that reward. If infants detect a change (or no change), they will be more likely to turn their head toward the rewarding stimulus than of they do not detect a change (or no change). The logic is that infants w ill correctly turn their head only when the number of items in the changing (or non-changing) array does not exceed their short-term memory capacity. In the second year of the project, the more sensitive of these two procedures will be used to determine the capacity of short-term memory in infants and whether infants, like adults, can remember multiple-feature objects just as easily as single-feature objects. These experiments will provide an important foundation for the study of short-term memory in infancy.